Tin is represented by "Sn" and has an oxidation number of +2, whereas Fluoride is represented as "F" and has an oxidation number of -1 (number of free electrons=-1).
Thus the chemical formula or Tin (II) fluoride would be SnF2 or `SnF_(2)`
The two i's in the parentheses indicate the charge of tin. Since tin is a metal (and also the first element in the compound) it will have a positive charge of 2 so
Sn = +2
Now Fluoride has a negative charge of 1 since it is in group 7a of the periodic table so...
F=-1 but since we need the compound to equal zero we will have to add 2 fluorine atoms and you will get the written compound
Symbol - Sn F
Valency- 2 1
When we cross multiply the symbols and valencies, we get the formula to be SnF2....(2 should be written at bottom of F)